Whether you need professional help depends on the size of your estate and the complexity of your wishes for how to distribute your assets.
Generally speaking, however, it makes sense to hire legal help to create your last will and any related trusts, as often times the cost to doing so is less than the cost of probate court and duress to your heirs in settling the estate themselves.
What is a Living Will?
What is the Difference Between a Will and a Trust?
How Much Does it Cost to Prepare a Will?